Glycogen Storage Disease Type IIIa, (GSD IIIa)

Glycogen storage disease (GSD) type IIIa is a disorder that affects the metabolism of glycogen.

Key Signs

Fatigue, Exercise intolerance, and Episodic hypoglycemic collapse

Age of Onset

1 to 4 yrs

Junior to adult onset


Autosomal Recessive

For autosomal recessive disorders, dogs with two copies of the variant are at risk of developing the condition. Dogs with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their puppies if bred.

Likelihood of the Condition

High likelihood

At risk dogs are highly likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a dog with GSD

Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about GSD

The clinical signs of GSD IIIa include fatigue, exercise intolerance, and hypoglycemic collapses caused by low blood sugar. Characteristic signs can typically be observed at around 14 months of age.

Management of affected puppies consists of a high-starch diet to prevent hypoglycemia at young ages and high-protein diets which may have a positive effect on cardiomyopathy associated with GSD IIIa. The use of medium-chain triglycerides has also shown positive therapeutic effects. Dietary therapies, however, do not prevent long-term complications of GSD IIIa.

For Breeders

Planning to breed a dog with this genetic variant?

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to occur. A carrier dog with one copy of the GSD mutation can be safely bred with a clear dog with no copies of the GSD mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the GSD mutation. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disease signs similar to the ones caused by the GSD mutation could develop due to a different genetic or clinical cause.

Technical Details

Gene AGL
Variant Deletion
Chromosome 6
Coordinate 50,050,451

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Gregory, B. L., Diane Shelton, G., Bali, D. S., Chen, Y. T., & Fyfe, J. C. (2007). Glycogen storage disease type IIIa in curly-coated retrievers. Journal of Veterinary Internal Medicine, 21(1), 40–46. View the article